There are many instances in which it is necessary or desirable to measure the temperature of a surface in situ, under conditions in which it is impractical or impossible to provide direct contact by a thermocouple or other form of mechanical probe. For example, it is not feasible to determine accurately the surface temperature of a deposit produced in a thin film-depositing reactor, either by contacting the film surface with a probe or by removing the deposit from the substrate.
Apparatus by which temperature measurements can be made remotely, and through optical means, are of course known in the art. One such instrument, for measuring the temperature of a target of unknown emissivity, is taught in Stein U.S. Pat. No. 4,708,493, issued Nov. 24, 1987. In accordance with it, first signals are derived from portions of radiation, from a thermally emitting target, occurring at two spaced wave lengths, and second signals are derived from reflected portions of two incident beams of radiation, at the same wave lengths. The derived signals are used to compute the temperature of the target.
Notwithstanding such prior art, a need exists for a relatively straight-forward and facile method by which the surface temperature of a sample can readily and accurately be determined in situ and without physical contact, and to provide apparatus for carrying out such a method; accordingly, it is the broad object of the invention to provide such a novel method and apparatus.
More specific objects of the invention are to provide such a method and apparatus which function through optical principles to determine the surface temperature of a target whose emissivity is unknown, and which afford means by which such emissivities can readily be determined.